Abnormal visual pathways will be studied in human post mortem brains, in a variety of mink brains, in Siamese cats and in hamsters and ferrets. The pathways from the lateral geniculate nucleus to the visual cortex will be studied by neuroanatomical and electrophysiological methods. The modifiability of the pathways by simple visual deprivation will be studied, and the developmental history of the abnormality will be studied in mammalian and also in nonmammalian brains. BIBLIOGRAPHIC REFERENCES: E. Geisert and R.W. Guillery. The laminar organization of layer IV stellate cells in area 17 of the tree shrew. Neuroscience Abstracts, 1976. J.K. Harting, V.A. Casagrande, J.H. Kaas and R.W. Guillery. The organization of retinotectal pathways in cats and primates. Neuroscience Abstracts, 1976.